Brief Summary

Brief Summary

The Eastern Cicada Killer (Sphecius speciosus) has been reported from nearly all states in the United States east of the continental divide, as well as southern Ontario (Canada) to the north and Guatemala, Honduras, and northeastern Mexico to the south (Holliday & Coelho 2006). Females dig nest burrows in well-drained soil, often forming large nesting aggregations, and provision nest cells with cicadas they capture and paralyze in nearby trees. Several studies have found that the number of cicadas provided to each offspring is fairly consistent, with sons given 1 (sometimes 2) cicadas and daughters given 2 (sometimes 3) cicadas regardless of cicada size. (Hastings et al. 2010 and references therein). Females are generally larger than male-- often over 4 cm in length--and they can provision their nests with cicadas more than 2.5 times their size (Coelho 1997).

Available data indicate no significant overall prey sex bias. However, Holliday et al. (2009) found that at sites where more than 50 cicada prey were recorded, the male to female ratio of 6 species brought to nests by Sphecius females varied between 0.524 and 2.259. At these sites, chi-square analysis revealed a significant male bias in overall prey sex ratio. The reported significant local variations in prey sex ratios are likely to be due to temporal variations in sex ratios of cicadas available to these opportunistic wasps. (Holliday et al. 2009)

Hastings et al. (2010) studied size-specific provisioning in S.speciosus in northern Florida. They found that individual female cicada killers at these locations exhibited size-specific prey selection. Small wasps brought only small cicadas to their nests, probably because they are unable to carry large cicadas in flight. Large wasps, which are not as constrained in this way, rarely provision their nests with small cicadas. It appears that these wasps selectively hunt the largest prey they can carry in flight. (Hastings et al. 2010) In contrast to the findings of Hastings et al, however, some previous studies in other areas have concluded that female S. speciosus hunted opportunistically, without regard to prey size. (Coelho 1997; Grant 2006). Hastings et al. suggest that this discrepancy may be explained at least in part by the fact that at these other locations the available prey were relatively uniform in size.

DNA sequence analyses by Hastings et al. (2008) have raised the possibility that S. convallis and S. speciosus may not actually be distinct species